PNH is an acquired defect of pluripotent hematopoietic stem cells in which mutations in the PIG-A (phosphatidylinositol glycan class A) gene result in a deficiency of glycosylphosphatidylinositol (GPI) anchor, thus preventing the presence of any of the proteins that require this anchor on the cell membrane, including CD55 and CD59, thus making derived RBCs highly sensitive to complement-mediated lysis [reviewed in (6)]. This evidence concerns the gene CD55 and paroxysmal nocturnal hemoglobinuria.